Process for inhibiting corrosion of metallic surfaces with cooling water containing phenol - aldehyde resins

ABSTRACT

WATER-SOLUBLE, PHENOL-ALDEHYDE COMPOSITIONS AS CORROSION INHIBITORS FOR INDUSTRIAL COOLING WATERS.

United States Patent O 3,687,610 PROCESS FOR INHIBITING CORROSION OF METALLIC SURFACES WITH COOLING WATER CONTAINING PHENOL ALDE- v HYDE RESINS Ian T. Gilson, Downers Grove, Edwin S. Troscinski, Oak

Lawn, Thomas C. Curtis, Country Club Hills, and

Robert G. Watson, La Grange, Ill., assiguors to Nalco Chemicals Company, Chicago, Ill.

No Drawing. Filed July 30, 1969, Ser. No. 846,227

Int. Cl. C23f 11/10 US. Cl. 212.7 Claims ABSTRACT OF THE DISCLOSURE Water-soluble, phenol-aldehyde compositions as corrosion inhibitors for industrial cooling waters.

INTRODUCTION One of the best known ways to inhibit corrosion of metallic surfaces, such as carbon steel, which are in contact with corrosive cooling Waters is to somehow increase the tendency of the metallic surface to form a protective metal oxide film. However, in the usual situation corrosion or rusting occurs because either the type or form of the oxide produced is non-protective or because the film forming reaction is too slow. Thus, soluble metal species are allowed to migrate too far from the surface to be of any appreciable value in forming a surface barrier to ionic and/or molecular corrodants or corrosion products. Dissolved oxygen in the aqueous environment in contact with the iron equipment or container then diffuses to the free metal surface more rapidly and high corrosion rates ensue.

If this diffusion could somehow be slowed down and controlled, corrosive attack would cease or be greatly reduced. Specifically, if, by some means formation of a thin, tightly bonded, uniform film of the proper type over the metal surface could be promoted, the metal system under attack from cooling water media would be less prone to corrode, or in many cases would be substantially non-corrosive where the exact nature of the film is not known.

In order to somehow aid formation of a protective metal oxide film, a chemical composition must not form strong complexes or chelates with soluble metal species which would increase the demand for metal in the cooling water and thereby increase corrosion rates. Yet, such a composition must be able to react with or absorb on metal or the metal oxides at the metal surface to control the crystalline-like growth and habit of the oxides. Also, a chemical treating agent when added to the cooling water system as a corrosion inhibiting substance must be able to reach the metal surface under attack or at least make a very close approach to the surface, certainly within the ionic double layer, while still in active form. In brief, a useful chemical anti-corrosive material should be able to help produce an ideal oxide film in a quick and eflicient manner by a facile, close approach to an iron surface to which it can attach itself or be in close proximity. The additive would then be able to adsorb or react with metal species just formed or those which are still in the process of being formed through the additives active sites, thereby enhancing filming on the surface to be protected.

The above problem is a particularly arduous one with which prior art materials have not been dependably able to cope. In some instances, the additive reagents while tying up in some manner the metal which has escaped from the surface of the corroding metal and through the ionic double layer, are thereby rendered almost immediately ineffective. In other words, such prior art material becomes quickly exhausted after some type of reaction or absorption with the metal ions, and is no longer effective in combating corrosion by promotion of protective iron oxide film. On the other hand, in some cases, substances added to cooling waters to inhibit corrosion of metal substances in contact with these liquids are so aggressive in their reaction with metal ions by some type of complexing or chelation that the concentration of metal ions in solution is rapidly depleted. This then has the adverse effect of shifting the equilibrium reaction at the metal surface and actually increasing the release of metal ions to the water. Metal attack is thereby increased. If, therefore, a corrosion inhibiting composition could be devised to somehow enhance formation of a protective metal oxide film on surfaces of corrodable metals, and obviate the just discussed problems, a substantial advance in the art would be made.

OBJECTS It is an object of this invention to provide cooling water compositions and method for their use.

Another object is to provide cooling water compositions which promote formation of a protective metal oxide film upon the surface of corrodable metals and thereby control the difiusion of oxygen to the free metal surface which is susceptible to its corrosive elfects.

Other objects will appear hereinafter.

INVENTION Invention summary The instant invention is directed to a process of inhibiting corrosion of metallic surfaces in contact with cooling Waters through the formation of a non-corrosive industrial cooling water composition. The non-corrosive industrial cooling water composition comprises a major part of an industrial water and minor portions of water-soluble phenolic resins.

The phenolic resins are formed through the reaction of an aldehyde and a phenol.

In a preferred embodiment of this invention, the noncorrosive industrial cooling water composition may also contain an additional additive. Such additional additives are polyvalent metal ions added as their salts.

The aldehydes The aldehydes used in preparing the phenolic resins of the invention may be generally described by the formula:

where R is selected from the group consisting of hydrogen and lower aliphatic groups having less than 5 carbon atoms.

Preferably the aldehydes are selected from the group comprising formaldehyde, acetaldehyde and propionaldebyde. The most preferred aldehyde is formaldehyde.

Phenols The phenols used in preparing the phenolic resins of this invention may be generally described by the formula:

Where X is selected from the group consisting of OH, -COOH, hydrogen, -SO H, -NH,;, and alkyl and alkylene radicals which have up to 8 carbon atoms.

The phenols which are used may have either the ortho or para position blocked so as to promote linearity and may also have meta substitution. Preferred phenols used in this invention are selected from the group comprising o-hydroxybenzoic acid, 2,4,6-trihydroxybenzoic, p-dihydroxy benzene, 1,2-dihydroxy benzene, 2,4-dihydroxybenzoic acid and 3,4,5-trihydroxybenzoic acid.

The reaction Aldehydes condense readily with phenols. The condensation primarily takes place through the ortho and/ or para positions to give polymers having aromatic rings linked together by methylene or oxydimethylene linkages. The mole ratio of phenol to aldehyde is about 1.0-2.0: 0.5-1.5. Preferably the mole ratio is 1.2:0.8. In many cases the mole ratio will depend on the catalyst used and the activity of the phenol.

There are a great many factors which can be deliberately varied in the reaction to introduce special characteristics to phenol-aldehyde reaction products.

One of the most critical variables is the pH of the catalyst. Other variables may include changes in time and temperature of reaction, manner of adding the reactants to the reaction system, the specific catalyst which is used, the specific type of phenol and aldehyde, and the use of modifiers during or after the reaction.

The catalysts which may be employed include many in number. Some examples are sulfuric acid, sodium hydroxide, formic acid, ammonia, trimethylene amine, sodium carbonate and hydrochloric acid. For a thorough discussion of catalysts, reference is made to The Chemistry of Synthetic Resins, Ellis, volume I, 1935, chapter 16 and which is incorporated herein by reference.

The temperature at which the reaction may be conducted may vary from -100" C.

However, regardless of the reaction conditions used, they must be so defined such that a water-soluble phenolaldehyde resin is produced.

Such Water-soluble resins are normally referred to as intermediate condensation products.

The intermediate condensation products are of low or moderate molecular weight and may he one of two types. The first is often called a resol and is formed by the reaction of excess formaldehyde with phenol. The mole ratio of formaldehyde to phenol in the presence of a base catalyst is about 1.5:1. It contains hydroxy methyl groups which condense further on heating.

The second type of intermediate is called a novolak. It arises from the reaction of less than equivalent amounts of formaldehyde with phenol. The mole ratio of formaldehyde to phenol in the presence of an acid catalyst is about 0.8:1. Upon the formation of this particular phenolic resin there are essentially no hydroxymethyl groups present for further condensation.

The novolaks may have molecular weights up to 1200- 1500. The resols have lower molecular weights and may vary from 300-700. The novolaks do not condense further without the addition of a catalyst and more formaldehyde. Hexamethylenetetramine is frequently used as a catalyst.

Because formaldehyde preferentially condenses at the ortho and/or para positions of phenol, it should be theoretically possible to prepare only linear, soluble high polymers from formaldehyde and a phenol with either an ortho or para position blocked.

For the purposes of this invention essentially linear and, therefore, water-soluble aldehyde-phenol resins are necessary. Such resins are defined to be the referred to intermediate condensation products given above and any (water soluble) dimer, trimer or oligomer products prepared via the phenol-aldehyde condensation reaction.

It is for this reason that the phenols which are used in this invention should have the ortho and/or para position blocked so as to promote linearity.

A preferred phenol-aldehyde resin is one which has 4 been bisnlfited. The sulfuric acid group may be introduced in various ways, i.e., sulfonation of the phenol prior to its reaction or sulfonation of the phenol-aldehyde resin subsequent to reaction.

A preferred phenol-aldehyde resin which has been bisulfited is l,2-dihydroxybenzene-formaldehyde.

Use of the invention The phenolic-aldehyde resins of this invention are readily used as corrosion inhibitors by preparing a non-corrosive industrial cooling water composition. This composition may be prepared by adding at least 20 p.p.m. of a linear, water-soluble phenol-aldehyde resin as defined above to a major proportion of an industrial water which is to be used as a cooling agent. In a preferred embodiment 20-500 p.p.m. of said composition are added. In a most preferred embodiment 30-100 ppm.

It has been discovered that the corrosion inhibiting properties of the phenolic-aldehyde resins decrease with increase in temperature. Therefore, preferred compositions of this invention include phenolic-aldehyde resins to which polyvalent metals in the form of their salts are added. Such compositions yield improved results over the sole use of phenolic-aldehyde resin at lower temperatures. However, what is more important is that such improvement is maintained, even at higher temperatures where the phenolic-aldehyde resins acting alone would be far less efficient.

The exact mechanism through which the use of the polyvalent metal maintains levels of lower temperature corrosion inhibition at higher temperatures is not known.

The referred to preferred compositions of this invention comprise 5-50 parts by weight of a water-soluble inorganic metal salt based on the metal ion per 100 parts of phenol-aldehyde. The water-soluble inorganic metal salt contains a multivalent metal ion selected from the group consisting of zinc, cadmium, cobalt, nickel and manganese. Preferably 25 parts of metal salt based on the metal ion are added per 100 parts of phenolaldehyde on a weight basis.

Preferred sources of the above ions are water-soluble salts of these metals such as halides, acetates, nitrates, and sulfates. Most preferred are the zinc and cobalt salts in any water-soluble form.

PREPARATION OF THE RESINS The following examples are given to illustrate the preparation of the resins of this invention and should not be construed as limiting it in any way.

EXAMPLE I Salicylic acid-formaldehyde resin was prepared by refluxing 138 grams of salicylic acid (1.0 M), 95 grams of a 37% solution of formaldehyde (1.16 M), 10 grams of water and 1 milliliter of a 97% formic acid. The refluxing was conducted for a 24-hour period at 85-90 C. in a resin kettle. After 24 hours the excess water was distilled 0E until the product became a sticky solid. The product was allowed to cool to room temperature and subsequently removed from the resin kettle. It was dried at 50 C. under vacuum for 24 hours. The product became solid and was ground to a fine powder and re-dried.

EXAMPLE H The preparation of 2,4-dihydroxybenzoic acid-formaldehyde resin was conducted by refluxing 2.5 grams of 2,4- dihydroxybenzoic acid (0.26 M), 10.5 grams of a 37% formaldehyde (0.13 M) 1 milliliter of a 97% formic acid and 40 grams of water. The reflux period was 5 hours. The reflux temperature was -85 C. At the termination of the reaction excess water was stripped from the reaction mixture under water vacuum at a temperature of 5055 C. Such stripping was conducted until the resulting powdery material was nearly dry. The product was removed from the flask and dried in a vacuum oven at 40 C.

EXAMPLE III In a 500 ml., three-necked flask equipped with stirrer and reflux condenser are placed 94 g. (1.0 M) phenol, 26 g. (0.25 M) anhydrous sodium bisulfite, 31.5 g. (0.25 M) anhydrous sodium sulfite, 75 g. (2.5 M) paraformaldehyde, and 11.3 g. water. An exothermic reaction occurs as the mass is stirred and the temperature rises to about 100 C. When the initial reaction subsides, the mixture is heated to reflux until a viscous syrup results. The syrup is then poured into a shallow glass tray and heated in a circulating air oven at 100 C. for 3 hours. The resulting product is illustrative of a bisulfited phenolaldehyde resin.

TABLE I.BLANK RUN Average corrosion loss Run pH inmilligrams The results relating to the extent of corrosion on coupons subjected to a cooling water treated with the composition taught by this invention are given below in Table II. The tests were conducted at F. for a period of 18 hours. Comparative effectiveness to the blank runs is indicated by the weight loss of the coupon.

TABLE II Additive Preparation Corrosion Test Data Test Additives in p.p.m. Percent Ratio of formalsitu improvement Corrosion Runs Catalyst dehyde ArOH pH ArOH Metal Zn over blank loss in mg.

5 ii lie acid 2-h drox benzoic acid HCOOH 1. 16 8 68 6. 2 8 cy y y nooon 1.16 7 86 2,6 HO O OH 1. 16 8 97 0. 6 H01 0. 8 7 81 3. 6 H01 2. 0 7 85 2. 9 (COOH): 0.8 7 82 3. 6 NaHSOa 2. 0 7 88 2. 4

2,4,6-trihydroxybenzoic acid- H01 8 8 95 1. 0 43 7 79 4. 1 HCO OH 0. 8 8 91 1. 7

1 3-djhydroxyhen one HO O OH 0. 8 8 89 2, 1

2,4-dihydroxybenzoic acid HCOO 8 8 100 25 94 1, 2 HCOOH 0.8 8 100 66 6. 7

3,4-5-trihydroxybenzotc acid HCOO 8 8 100 95 0. 9

SulIonated 3,4,5-trlhydroxybenzoic acid HCOO 8 7 1, 000 67 6. 5 HCOOH 0. 83 8 100 25 89 2. 2

z-hydroxy, 5-sulfonobenzoic acid HGOOH 0.8 8 100 25 90 1 9 2,4-dih dro benzaldeh de HCOOH 0.8 8 100 25 92 1. e y W y NaHSOs as s 100 25 94 1. 2

EVALUATION OF THE INVENTION In order to demonstrate the effectiveness of the corrosion composition of this invention tests were conducted using mild steel coupons having 2" x x A dimensions as test specimens. The steel coupons were subjected to a moderately hard water whose composition was such as to simulate a typical cooling water. The composition of the cooling was as follows: 250 p.p.m. Ca++. 150 p.p.m. Mg++ and 55 p.p.m. total alkalinity as CaCO 600 p.p.m. Cl. as NaCl; 500 p.p.m. SO as 'Na SO .009 p.p.m. Fe++, 0.3 p.p.m. Al 3.1 p.p.m. SiO 0.1 p.p.m F-

The tests were conducted in accordance with the following procedure:

A sand-blasted coupon measuring x 2 x $1 inches was pretreated in a 1000 p.p.m. solution of sodium nitrite for 24 hours. The coupon was weighed and suspended for 18 hours in a 600 ml. beaker containing 500 ml. of test solution. The test solution was agitated at 1725 r.p.m. with a glass propeller bearing two blades 9 mm. in diameter.

After exposure, the coupon was removed and cleaned by scrubbing in water and by immersing for seconds in inhibited HCl. The cleaned coupon was then weighed and then reimmersed in inhibited HCl and reweighed to obtain an estimate of the metal loss due to cleaning.

The corrosion loss was calculated from the following formula:

Corrosion Loss (Initial weight) (clean weight)'+ (cleaning loss) For a basic of comparison, Table I given directly below shows results represeting specimen subjection to treatment free water at ambient pressure and temperature for an 18 hour period.

An inspection of Table II demonstrates quite aptly that the corrosion inhibitors taught by this invention comprising phenolic-aldehyde resins give excellent results.

CONCLUSION Obviously, many modifications and variations of the invention as hereinbefore set forth may be made without departing from the spirit and scope thereof. Therefore, only such limitations should be imposed as are indicated in the appended claims.

Having described our invention we hereby claim:

1. A process for inhibiting corrosion and fouling of metallic surfaces in contact with cooling waters consisting essentially of maintaining contact of said surfaces with said cooling waters containing from 20 p.p.m. to 500 p.p.m. of a chelating system to complex water dispersible metallic species existing in such cooling water which chelating system comprises:

(1) a water-soluble phenolic resin formed by the reaction of:

(A) from 0.5 to 1.5 moles of an aldehyde having the formula- 1| R-O-H where R is selected from the group consisting of hydrogen and lower aliphatic groups having less than 5 carbon atoms, and (B) from 1.2 to 2 moles of an ortho and/or para blocked phenol of the formula where X is selected from the group consisting of -OH, -COOH, hydrogen, -SO H, -NH and alkyl and alkylene radicals which have up to 8 carbon atoms.

2. The process of claim 1 where the phenol is selected from the group comprising o-hydroxybenzoic acid, 2,4,6- trihydroxy-benzoic acid, p-dihydroxy benzene, 1,2-dihydroxy benzene, 2,4-dihydroxybenzoic acid and 3,4,5-trihydroxybenzoic acid.

3. The process of claim 1 where said cooling water contains 30-100 ppm. of said chelating agent.

4. The process of claim 1 Where the aldehyde is selected from the group comprising formaldehyde, acetaldehyde and propionaldehyde.

5. The process of claim 2 where the aldehyde is formaldehyde.

6. A process for inhibiting corrosion and fouling of metallic surfaces in contact with cooling waters consisting essentially of maintaining contact of said surfaces with said cooling waters containing from 20 ppm. to 500 ppm. of a chelating system to complex water dispersible metallic species existing in such cooling water which chelating system comprises:

(I) a water-soluble phenolic resin formed by the reaction of:

(A) from 0.5 to 1.5 moles of an aldehyde having the formula- I R-(J-H where R is selected from the group consisting of hydrogen and lower aliphatic groups having less than carbon atoms, and

(B) from 1.2 to 2 moles of an ortho and/ or para block phenol of the formula:

where X is selected from the group consisting of -0I-I, -COOH, hydrogen, -SO H, -NH

and alkyl and alkylene radicals which have up to 8 carbon atoms, and

(II) a water-soluble inorganic metal salt having a concentration of 5-50 parts by weight per parts of said water-soluble phenolic resin based on metal ion, where said metal ion is multi-valent metal ion selected from the group consisting of zinc and cobalt.

7. The process of claim 6 where the phenol is selected from the group comprising o-hydroxybenzoic acid, 2,4,6- trihydroxy-benzoic acid, p-dihydroxy benzene, 1,2-dihydroxy benzene, 2,4-dihydroxybenzoic acid and 3,4,5-trihydroxybenzoic acid, and the metal ion is zinc.

8. The process of claim 6 where said cooling water contains 30-100 ppm. of said chelating agent.

9. The process of claim 7 where the aldehyde is selected from the group comprising formaldehyde, acetaldehyde and propionaldehyde.

10. The process of claim 9 where the aldehyde is formaldehyde.

References Cited UNITED STATES PATENTS 2,165,852 7/1939 Harmon et. a1 21-2.7 2,285,750 6/1942 Swain 252- 2,341,907 2/1944 Cheetham et al 252-180 3,331,773 7/1967 Gunderson 210-58 3,530,569 9/1970 Wilson 106-14 2,758,101 8/1956 Shappell 260-293 2,763,680 9/1956 Sallmann 252-180 3,298,999 1/ 1967 Kiriyama 260-293 3,505,238 4/1970 Liddell 252-180 2,885,299 5/1959 Labino 260-293 2,904,875 9/ 1959 Trigg 260-29.4 2,981,710 4/1961 Hoeuel 260-293 3,133,034 5/ 1964 St. Clair 260-293 3,397,077 8/ 1968 Boller 260-294 3,410,818 11/1968 Yuroick et a1. 260-293 3,484,837 12/ 1969 Odom et a1. 260-294 40 DONALD J. ARNOLD, Primary Examiner US. Cl. X.R. 

